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Salinity Sensor Experiment: Temperature Dependence of Conductivity in Dilute Aqueous
8
3.
Connect the Salinity Sensor to the data acquisition interface. Support the Salinity
Sensor Probe with a clamp that is mounted on a base and support rod (see Figure
1). Place the hot plate with magnetic stirrer below the tip of the probe.
4.
Start the data acquisition program. Set up a graph display that shows conductivity
on the vertical axis and temperature on the horizontal axis.
5.
Put the beaker with the first 200 ml sample on the hot plate. Arrange the Salinity
Sensor Probe so that at least 5 cm of the tip is in the solution.
6.
Turn on the hot plate and magnetic stirrer. The heat and the stirring controls
should be set to a mid-range value.
7.
Start recording data. Tap the Salinity Sensor Probe occasionally to avoid the for-
mation of air bubbles in the probe’s cell. When the temperature of the solution
reaches 50 °C, stop recording data.
8.
Remove the Salinity Sensor Probe from the first sample. Rinse the end of the
probe with distilled water.
9.
Repeat the data collection process with the other two samples.
Data Analysis
1.
Autoscale the graph display and select Run #1.
2.
Use the data analysis features of the data acquisition software to select a “Linear
Fit” for the data. Determine the slope of the first run of data.
3.
Use the Smart Cursor feature of the software to find the conductivity at the place
in the graph where the temperature is 25 °C.
4.
Divide the slope by the value of the conductivity at 25 °C. Convert the answer to
a percentage to determine ‘percent change/°C’. Record your result in the Data
Table.
5.
Repeat the data analysis process for the other runs of data.
Data Table
Questions
1.
Describe the effect of temperature on the conductivity of the solutions.
2.
Compare the experimentally determined values of percent change per degree C at
25 °C for the samples.
3.
What are some factors that affect the conductivity of a solution?
Sample
percent change/ °C at 25 °C
0.1% NaCl (1000 ppm)
0.4% NaCl (4000 ppm)
0.005 M NaOH (1000 ppm)
Calibration is not needed
for this experiment.
